In the tiny New York town of LeRoy, one thing is for sure; since October, 16 people suddenly have developed uncontrollable twitching and verbal tics.

Three months later, they -- and the rest of the town -- are still wondering why.

Doctors have diagnosed most ofthem with conversion disorder, saying that stress is the likely root of their physical problems.

"What happens is there traditionally some kind of stress or multiple stressors that provoke a physical reaction within the body," said Dr. Jennifer McVige, a neurologist who has evaluated several of the teens. "This is unconscious, it is not done purposefully and it's almost like ... the stress wells up in your body has to come out in some way shape or form."

But the diagnosis has done nothing to explain why so many people from the same small town -- 14 teenage girls, a teenage boy and a 36-year-old woman -- started displaying these symptoms within the same time period.

All of the teens attend LeRoy Junior-Senior High School, so the attention has turned there. School officials say everything is safe, but environmental organizations and some parents aren't so sure.

The medical mystery in LeRoy has attracted the attention of activist and investigator Erin Brockovich, who came to the village of 8,000 people in western New York after learning about a 41-year-old toxic spill a few miles from the school.

Brockovich and her longtime associate Bob Bowcock, an engineer who has been in the water treatment and testing business for more than 30 years, arrived in LeRoy after receiving an email note from a parent of one of the affected teens. The two suspect that the illnesses are related to the cyanide and trichloroethylene (TCE) that was spilled during the December 1970 train wreck.

Brockovich and Bowcock are conducting their own environmental tests to determine whether the chemicals were cleaned up properly.

The school along with the Environmental Protection Agency and the New York departments of health and environmental conservation said they already tested the area, and there is no evidence that the site is to blame for this mystery ailment in the students.

"All of these agencies and professionals from these agencies have assured us that our school is safe," LeRoy school district Superintendent Kim M. Cox wrote in a letter to the community this week. "There is no evidence of an environmental or infectious cause. Environmental causes would not discriminate (regarding who becomes infected)."

She said the school hired an independent firm in December to test for volatile compounds, and the report found nothing dangerous. An air quality test also was normal, she wrote.

Still parents are worried and upset.

"They say that they are out there looking out for our girls, and are sympathetic to our girls but what is it? Actions speak louder than words." Lana Clark, whose daughter has tics, told HLN TV. " And I don't see a lot of action,"

Erin Brockovich gained fame after the 2000 movie bearing her name told the story of how she, as a file clerk at a law firm, established that a toxic chemical from a power company compressor station leaked into the groundwater of a nearby town, compromising the health of hundreds.

She thinks something similar might be happening in LeRoy. She and Bowcock started their investigation in late January at the train derailment site, which is about 3 ½ miles from where the teenagers go to school.

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According to a 1999 report from the EPA, about 30,000 gallons of trichloroethylene (TCE), a potentially harmful chemical used primarily as a cleaning solvent, and 1 ton of cyanide crystals spilled from ruptured tank cars.

The report said the railroad company, Lehigh Valley Railroad, tried to get rid of chemical odors at the site by using 1,000,000 gallons of water to flush the chemical into trenches, for four months beginning in March 1971.

The EPA and the New York Department of Health found TCE in 50 wells east or southeast of the site when they ran tests between 1990 and 1994. They installed water treatment systems at 37 of the wells where the levels of TCE were above the maximum standard.

Amid pressure from the students' parents and Brockovich, the EPA announced Tuesday that it is going to test soil that sits in barrels near the site of the spill that observers, including Bowcock, have said are leaking dirt. The dirt and rock was extracted from the ground when the New York Department of Environmental Conservation drilled monitoring wells in the 1990s.

"Having found it in the condition that we found it in, having looked at the fact that EPA has been absent from this process for at least four years that we know of, I think it's ... time to start over and test. Test, get some independent folks in there, and get this done," Bowcock said.

Bowcock told HLN's Dr. Drew Pinsky that he had taken water samples in town but was prevented by authorities from getting samples at the school. It will take at least three weeks before results come in, he said.

Medical authorities have cast doubt on whether TCE could cause health effects more than 40 years later, particularly in the form of uncontrollable tics and verbal outbursts. Toxicologist Dr. LuAnn White explained that a person would have to be exposed to very high doses of TCE for an extended period or get a huge dose at one time to become sick.

"In order to relate health effects, it is necessary to know the concentration and the duration and frequency of exposure," said White, director of the Tulane Center for Applied Environmental Public Health Sciences.

She said TCE is rapidly cleared from the body, so after a few days it would not show up in blood or urine tests. But she said any symptoms would also go away.

TCE is linked to cancer, though not a proven carcinogen, she said.

Another area of concern for environmental groups in LeRoy are natural gas wells on school property. The natural gas from the wells is used to heat school system buildings. The wells use a controversial technique called fracking, which shoots a chemical mixture into the earth to force out the gas. In July 2011, some of the tanks at the well sites leaked fluid on to athletic fields. Some trees died. The school was told to dig up the affected soil, according to documents obtained by CNN.

Judy Braiman, the president of the Empire State Consumer Project, a nonprofit environmental advocacy group, wants more testing at the school. She said the independent tests already commissioned by the school and done by the government "just sort of skimmed the surface."

New patient, not a typical case

Prior to this week, these strange symptoms had been confined to the teenagers from LeRoy Junior-Senior High School. That all changed on Tuesday when a 36-year-old woman told CNN that she also has been diagnosed with conversion disorder.

Fitzsimmons believes that she has conversion disorder but she's keeping an open mind as federal and independent investigators look into possible environmental causes.

She told CNN that as a youngster she had often swum in the waters of a large quarry within 100 yards of the toxic spill site. It was a place where teenagers used to hang out during the summer. None of the sick other patients have said they had been to the quarry.

Fitzsimmons said even if the cause is determined to be environmental, it won't solve her main question: Will she ever get better?

"At this point I have to have faith in my doctors. All the CAT scans MRIs I have done have come back with in the normal range. So if it ends up being environmental then does that mean I don't have hope of getting better? These are thoughts that go through my head," she said.

'I can't do what I love'

Thera Sanchez was a cheerleader, an honor roll student, and planning her college future when she woke up from a nap in October. That's when everything changed.

"I couldn't stop stuttering," she told CNN's Jason Carroll.

Thera Sanchez is one of 16 people from LeRoy, N.Y., who started having uncontrollable tics in October.

Doctors told Sanchez that her condition was brought on by stress and she would get better. But once the stuttering ended, it soon gave way to uncontrollable twitching.

"The stuttering you know took over contorting her left side of her mouth and neck," her mother Melisa Phillips said.

She took Sanchez to the hospital in mid-October, and that's when a nurse told her that she wasn't the only one who had been brought to the hospital with the condition.

"She had said, 'Not to alarm you, but somebody needs to contact somebody because you're the fourth girl in a week to come in with this,' " Phillips said.

Like most of the others, Sanchez was diagnosed with conversion disorder. The girls were from different grades; some knew each other, others did not. Sanchez doesn't believe that stress triggered her condition, and her mother worries whether time is on their side.

"She does not have time for ... guesswork or anything like that," Phillips said. "She's deteriorating."

For now, Sanchez's life is on hold while doctors try to figure out how to treat her condition.

"It's heartbreaking to me to be honest knowing I can't do what I love," she said.

Whatever the cause, many experts in the medical community have expressed skepticism that these symptoms could be the result of toxins in the environment.

"What's in our food, what's in our water, what's in our air, is a massive cause of disease, but probably not this kind of disease," said mental health expert Dr. Charles Raison. "You don't see these sudden onsets of things, especially if (toxins) have been in the environment for a long period time. It would really be a radical discovery if someone could prove to a reasonable doubt that it was something in the water or the air."

Still, he cautioned that whenever there is a cluster of cases, it is necessary to thoroughly test for environmental or infectious causes.

Until doctors can figure out what exactly is triggering the symptoms and how to treat the disorder, Sanchez and the others can only hope that one day they will wake up and be themselves again.